monoCamera codegen error: Handle Classes in top-level outputs are not supported in MATLAB Coder

monoCamera is defined in https://www.mathworks.com/help/driving/ref/monocamera.html?s_tid=srchtitle. and have codegen capability. I try to generate the C++ object with code below:

function sensor = gen_camera(focalLength, principalPoint,imageSize, height,pitch,roll) %#codegen
	coder.inline('never');
	intrinsics = cameraIntrinsics(focalLength,principalPoint,imageSize);
	sensor = monoCamera(intrinsics, height, 'Pitch', pitch, 'Roll', roll);
end

and codegen reports error:

cfg = coder.config('lib');
cfg.HardwareImplementation.ProdHWDeviceType = 'Intel->x86-64 (Linux 64)';
cfg.TargetLang = "C++";
cfg.CppNamespace = 'camera';
cfg.CppNamespaceForMathworksCode = 'MatlabCV';
cfg.HeaderGuardStyle = "UsePragmaOnce";
cfg.PostCodeGenCommand = 'packNGo(buildInfo)';
>> codegen  -config cfg -report -o cameraVision gen_camera -args {focalLength, principalPoint,imageSize, height,pitch,roll}
??? Handle Classes in top-level outputs are not supported in MATLAB Coder. Output parameter 'sensor'
contains a handle class.

Anyway to solve this issue?

Answer 1

[Aghamarsh Varanasi]

Hi Li Chen,

‘sensor' is a Handle class object of the class ‘monoCamera’. A handle class object cannot be an entry-point (top level) function input or output.

Refer this documentation page to declare a MATLAB class that supports codegen.

If the purpose of ‘sensor’ handle class object is just to pass data from one function to another, you could instead convert ‘sensor’ to a structure and pass it as an output argument to the function ‘gen_camera’.

sensor = struct(sensor); 

You can add this line at the end of your fucntion ‘gen_camera’.

[li chen]

After adding this line, I got error:

???Struct with one argument is not supported for code generation.

I'm using Matlab R2020b